3 Answers
3

If the jars are properly sealed the vacuum in the jar and the waxed edge will hold the lid safely sealed. Undisturbed those jars will remain sealed until they are opened. The ring will reduce the risk of "unintentional" opening and that is really all the ring does. There are two real advantages to removing the ring once the seal is set.

If something spoils in the jar it is likely to pop the lid open. Spoilage would give off gasses that would increase the pressure inside the jar and break the seal. This is more obvious if the ring has been removed.

When it comes to juices, unintended fermentation is an issue. Even if raised to a temperature that is expected to kill yeast sometimes some of the little buggers get through and will ferment juices. Without the ring the fermentation breaks the seal. This prevents jars from exploding under pressure (yes, it can happen). I had a grandmother who would can grape juice, but did not want 'wine'. When the lids popped it identified the jars that had fermented, and which could be disposed (sometimes not the way grandma intended).

I prefer to leave the rings on as when the jars get stacked up in the pantry jars can get jostled and a lid may get accidentally opened, but there is nothing "wrong" with taking them off.

Note if you want to store it with the rings, you should take them off after the jar has cooled and let it dry out for a day or two. Keeping the ring on without doing so could lead to rust forming inside, and could compromise the seal. I prefer using the plastic caps one everything is dry. It serves the same purpose as the ring, but provides a nice cap when opening the jar. Makes for a good presentation when giving away canned goods as gifts, too.
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JSMAug 18 '14 at 16:15

On the other hand, you'll want the ring once you open the jar, so it's nice for it to just be there, especially if you're giving canned goods as gifts.
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Jefromi♦Aug 26 '14 at 18:02